Four American journalists were arrested in Bahrain Sunday while covering the anniversary of mass protests in that country, the Committee to Protect Journalists announced today.

Anna Therese Day, a freelancer who has contributed to The Huffington Post, was identified as among those arrested in a statement released by the families of one of the journalists, according to the Committee to Protect Journalists. The other three were not identified.

In a statement, Bahrain's Ministry of Interior said the Americans were arrested for "entering the country under the false pretense of tourism and failing to register with the appropriate authorities," according to CPJ:

The Interior Ministry said police had arrested one journalist, whose name they did not provide, in the village of Sitra, and alleged he had participated in riots and attacks against police there. Three other journalists whose names the Interior Ministry did not release were subsequently arrested at a nearby checkpoint, the ministry said, adding that the four would be referred to the prosecutor general's office.

As of December 2015, Bahrain had imprisoned five journalists, all of whom were freelancers for Internet publications. Reporters Without Borders ranked Bahrain 163 out of 180 countries in its World Press Freedom Index, an assessment that makes it one of the most hostile countries for journalism worldwide.

Foreign journalists seeking to work in Bahrain have to have special permission to do so, according to The Associated Press:

The island kingdom allows citizens of many countries, including the U.S., to get a tourist visa on arrival. Obtaining a media visa takes several days, and activists say Bahrain has denied media visas for some journalists since the 2011 protests.

Sherif Mansour, the Middle East and North Africa program coordinator for CPJ, called for the release of Day and the others in a statement.

It is sad that the fifth anniversary of the 2011 protests has been marked by the arrest of yet more journalists in Bahrain, which has since become one of the worst jailers of journalists in the Arab world.